Implement into OPL JSON extension of field "pointing"

From Marc's email on Sep 19, 2025:

As an extension of one of the fields that we are now including in the OPLs: “pointing”. To fill in that field, we have put together a list of pointing “modes” that you can find attached.

We have included what we believe are high-level pointing modes and for the time being we are not linking them to any PTR snippet and are not meant to be used for this purpose (at least yet) therefore the field is indented to assist the Observation Timeline Harmonisation process when scheduling your observations.

Please take a look and feel free to provide feedback before the SOWG Splinter for which I just sent an email some minutes ago. Feedback can also be provided at that meeting but it will not the scope of the meeting.OPL_POINTING_MODE_DEFINITIONS_V1.json